A standard web-cutting machine comprises a pair of cylindrical drums rotatable about parallel and normally vertically spaced axes as described in "Querschneider an Papierverarbeitungsmaschinen" (Allaemeine Papierrundschau April 1965). Each drum is normally formed with at least one axially extending groove in which is set a blade. The drums are rotated or moved synchronously so that the blades periodically come together, cutting through a web passing horizontally between the drums. The blades can be straight, in which case they engage the workpiece web along its entire width simultaneously. It is also known to make them somewhat helical so that they engage the workpiece at a point that moves from one side to the other of the workpiece as it passes between the drums, forming what ends up as a perfectly straight perpendicular cut, produced by coordination of the advance rate of the workpiece, the peripheral velocities of the blades, and the angular dimension of the blade helix. Such systems are described in German 4,240,232 of Titz, 4,321,163 of Pfirrmann, 195 45 003 of Stitz, and 89 00 516 assigned to BHS Ag.
Obviously these blades must meet perfectly in order to cut smoothly and form a neat edge on the sheets produced. The standard procedure is therefore to provide some form of adjustment. In the simplest system the blade is simply bolted to the drum via slots so it can be positioned before the bolts are torqued down. For finer control of the adjustment, bolts threaded or otherwise seated in the drum bear on rear edges of the blade so that when rotated they displace the blade tangentially and, if necessary, radially into the desired position. Once properly positioned the blades are bolted tightly in place. Such systems are described in U.S. Pat. No. 4,159,661 of Russell, German utility model 195 12 032 assigned to Will GmbH, European 0,193,693 of Takenaka, and European 0,736,362 of Gross.
Even these last-described systems present considerable difficulties in setup. In particular when the blades have been taken out and sharpened, it is just as difficult to align them on reinstallation as it is with new machines. With the screw-adjuster systems all the screws must be advanced and then the fit tested, the screws readjusted, and so on. Thus the down time is considerable.